Slurry pump having impeller flow elements and a flow directing device

ABSTRACT

A pump assembly and components therefor including an impeller which has flow inducer elements on an inner surface of a front shroud thereof, a flow directing device or strainer having passageways for delivering material to the impeller and at least one flow circulating passageway and a pump casing having an intake section with flow distribution vanes in the region of a feed opening adjacent the intake section.

TECHNICAL FIELD

This invention relates generally to pumps and more particularly to pumpsof the type which include for example sump pumps, submersible pumps, jetpumps and the like.

BACKGROUND ART

Centrifugal sump pumps find application in a wide range of industriesincluding mining. Mining applications for sump pumps typically includepumping a mixture of water with mineral particles of different particlesizes and densities. This mixture is commonly referred to as slurry andbecause it contains solids it can be very abrasive. Consequently sumppumps used in mining in most instances are constructed from wearresistant materials.

Sump pumps used in mining applications are typically mounted on beams ontop of a usually wide and relative shallow sump or pit. A driving motorand pump bearings are all disposed above floor level so they are notsubmerged thereby ensuring longer life of these parts. The pumpingelements are attached to a vertical shaft and are normally positioned atthe end of a long cantilevered shaft and near to or close to the bottomof the sump. The sumps are normally located strategically within theplant and sunk below the normal floor level with shallow angledsurrounding floor areas so that all leakage, spillage or slurry productswill gravitate directly into the sump. Depending on the size of the sumpin relation to the sump pump, the type of particles and their densityand the flow rate of slurry required from the sump, some percentage ofparticles will naturally collect in the bottom of the sump and, oncesettled out of the water, they tend not be picked up again by the sumppump. Over time these particles build-up and can block the sump,particularly if the particles tend to bind together.

A conventional sump pump apparatus is illustrated in FIG. 1 which is aschematic sectional side elevation thereof. The sump pump 10 as shownincludes a pump casing 12 with an impeller 14 disposed therein. Theimpeller 14 is operatively connected to a drive shaft 16 which in thenormal pump operating position is generally vertically arranged. Thedrive shaft 16 is supported by a bearing assembly 18 and is operativelyconnected to a driving motor (not shown). A column 20 surrounds thedrive shaft 16.

The pump casing 12 has two inlets to a pump chamber 21 within thecasing, namely a first inlet 22 and a second inlet 24. A first strainer26 is provided at the first inlet 22 and a second strainer 28 at thesecond inlet 24. A discharge pipe 25 extends from the pump casing 12.When in use the first inlet 22 and strainer 26 is positioned close tothe bottom of the sump with the second inlet 24 located above it. Thestrainers 26, 28 function to prevent the ingress of large particulatematter into direct contact with the impeller 14 which is housed in thecasing 12. Such particulates can jam the rotation of the impeller andpossibly damage the impeller, leading to an early failure of the sumppump. However the impeller can still become damaged by a build-up offiner particulates within the casing.

In order to try and alleviate the problems of particle build up both inthe sump pit and within the conventional sump pump housing as referredto above, it has been proposed to provide agitators which somehow extendseparately into the sump pit, or another co-axial type of agitator whichcan be fitted to an extension shaft which projects below the secondinlet 24. However the effectiveness of known agitators can varyconsiderably and, because agitators tend to wear rapidly, theirefficiency can be rapidly diminished during use. In some circumstances,trials have been made in which the lower sump pump inlet 22 iscompletely closed off, with the slurry only entering via the upper pumpinlet 24. While this may prevent jamming the rotation of the impeller,this may also limit the flow that can be pumped, which in turn mayresult in sump overflow.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a pump impeller havinga rotational axis and including:

-   -   a hub,    -   a back shroud extending from the hub, and    -   a front shroud,        wherein each of the shrouds has an inner surface and an outer        surface, the impeller also having:    -   a plurality of pumping vanes extending between the respective        inner surfaces of the shrouds, and    -   an impeller inlet opening in the front shroud coaxial with the        rotation axis of the impeller,

wherein the impeller includes one or more inducer elements which extendfrom the inner surface of the front shroud towards the rotation axis andwhich are positioned adjacent the impeller inlet opening.

During use of such an impeller, when the impeller is caused to rotatethe inducer elements can assist the uplift of particulate matter intothe region of the pumping vanes and thus the subsequent removal of thematter from adjacent the impeller inlet opening. In situations such asclearing settled solids from a sump pit, the particles may be relativelylarge in size or naturally heavy or dense, and the inducer elements canassist with the removal of such settled material.

In one embodiment the impeller can include a plurality of inducerelements, the said elements are arranged circumferentially about theimpeller inlet opening. In other forms there may be only one inducerelement, for example a screw-form or helix shaped protrusion on theinside surface of the impeller front shroud.

In one embodiment a plurality of flow generating elements can bearranged in a spaced apart fashion and extending from the outer surfaceof the front shroud in the region of the impeller opening. Thearrangement is such that in use the flow generating elements are adaptedto cause a recirculating flow in the region of the pump inlet andexternally thereof.

In one embodiment the front shroud can include an annular wall portionand a projecting wall portion depending therefrom, the projecting wallportion arranged to extend away from the pumping vanes to terminate at afree end, the impeller inlet opening being in the region of the free endso as to define an impeller intake region between the impeller inletopening and the pumping vanes.

In one embodiment the projecting wall portion can taper inwardly fromthe annular wall portion when moving in a direction towards the freeend. In one form of this, the projecting wall portion may be curved.

In one embodiment the impeller can also have a further group of pumpingvanes on the outer surface of the back shroud arranged in spacedrelation from one another. In one form of this, each further pumpingvane can be curved with one end adjacent the back shroud outerperipheral edge and extending inwardly therefrom towards the hub.

In one embodiment of the impeller, in situations where there are aplurality of inducer elements, the said elements can be in the form ofvanes. In one form the vanes can be generally of an aerofoil shape. Inone arrangement, the vanes can be located on the inner surface of theprojecting wall portion adjacent the free end.

In one embodiment of the impeller, in situations where there is aplurality of flow generating elements, the said elements can also in theform of vanes. In one form these vanes can also generally be of anaerofoil shape. In one arrangement, these vanes can be located on theouter surface of the projecting wall portion adjacent the free end.

The inducer elements are arranged such that in use, when the impeller isrotating they assist in creating a swirling flow adjacent to andexternally of the impeller inlet. In one embodiment the inducer elementsare in the form of vanes extending from the inner surface of the frontshroud, each having free edge portion which is spaced from the centralrotation axis. In one arrangement of this, each vane extends towards therotation axis to a point about half the radius of the impeller opening.The inducer vanes may be of any suitable shape and not necessarilyaerofoil-shaped. The vanes may extend generally radially or may beinclined to the normal radial direction. Any suitable number of inducerelements may be provided, and in one embodiment two are arranged indiametric opposed position at the impeller flow intake region.

In a second aspect the present invention provides a flow directingdevice, in use for directing material in relation to an adjacent movingimpeller, the device including a main body having an inner side and anouter side, a plurality of passageways extending between the inner sideand the outer side of the main body, at least one passageway providingfor the in use delivery of material to an opening of the impeller and atleast one other passageway providing for the in use circulation of aflow of material past the impeller.

In response to the in use rotation of the adjacent impeller, such adevice can create a recirculation flow pattern of slurry material aimedto cause the disturbance of settled particulate matter in the region ofthe impeller, which can be important for clearing settled solids from asump pit when the particles may be large in size or naturally heavy ordense. Once the settled solid material is disturbed, the flow directingdevice also has a separate passageway which leads to the opening of theimpeller where the pumping action draws the fluidised slurry materialinto the impeller for removal. The device therefore performs a dualfunction and is ideally suited to pumping applications in areas wheresolids may have been allowed to settle for some time.

In one form, the flow directing device can include a chamber adjacentthe inner side of the main body, said passageways communicating withsaid chamber. In one form the device can include a plurality of saiddelivery passageways and a plurality of said circulation passageways.

In one embodiment, a plurality of said passageways can be generallyannular in shape when viewed in a horizontal cross-section and arrangedsubstantially concentrically with respect to one another. In one form ofthis, the or each circulation passageway may be disposed radiallyoutwardly with respect to the or each delivery passageway.

In one embodiment of the flow directing device, the main body includes aperipheral side wall section and a plurality of concentrically arrangedring shaped elements operatively connected together and operativelyconnected to the peripheral side wall section, the annular spacesbetween the ring shaped elements providing for said passageways. In oneform of this, one of said ring shaped elements can include a skirtportion at the outer side of the main body which provides for a partialbarrier between the circulation passageway(s) and the deliverypassageway(s).

In a third aspect the present invention provides a flow directing devicewhich is arranged to direct two material flows in response to therelative movement of an adjacent impeller, the flows being:

-   -   a mixing flow in which material is mixed and agitated in        response to the movement of the adjacent impeller in use; and    -   a pumping flow in which material is passed through the adjacent        impeller in use and pumped to another location.

Such a device has operational advantages as have already been describedherein for the device of the second aspect.

In a fourth aspect the present invention provides a pump casingincluding:

-   -   a main body section having a pumping chamber therein, and a        discharge outlet extending from the pumping chamber;    -   a strainer section having an intake region therein, with one or        more inlets located at the intake region; and    -   a feed opening between the intake region and the pumping        chamber;        wherein a plurality of flow distribution vanes are positioned in        the region of the feed opening.

In response to the in use rotation of the adjacent impeller, the flowdistribution vane(s) in the pump casing can assist with the efficientdelivery of slurry material into the pumping chamber, where the pumpingaction draws the fluidised slurry material into the impeller forremoval. The vane(s) can reduce swirl and improve the efficiency ofdelivery of the slurry flow to the in use outer surface of the backshroud of the impeller.

In one embodiment having a plurality of inlets, said flow distributionvanes can extend from the inlets and be arranged in spaced-apartrelation.

In one embodiment the main body section can include a back wall and aperipheral side wall depending from said back wall, wherein the intakeregion extends from said back wall in a direction opposite to theperipheral side wall.

In one embodiment, the intake region can include a generallyfrusto-conical inner side surface, having said inlets being disposed inspaced apart relation around said frusto-conical section.

In one embodiment, the inlets can be elongate holes or slots arranged inthe inner side surface of the intake region.

In one embodiment of the pump casing, the pumping chamber can begenerally volute in configuration.

In a fifth aspect the present invention provides a pump impeller havinga rotational axis and including:

-   -   a hub,    -   a back shroud extending from the hub, and    -   a front shroud,        wherein each of the shrouds has an inner surface and an outer        surface, the impeller also having:    -   a plurality of pumping vanes extending between the respective        inner surfaces of the shrouds, and    -   an impeller inlet opening in the front shroud coaxial with the        rotation axis of the impeller,

wherein the impeller includes one or more flow generating elements whichextend from the outer surface of the front shroud in the region of theimpeller opening.

In one embodiment, the pump impeller of the fifth aspect can beotherwise as claimed in the first aspect.

In a sixth aspect the present invention provides a pump assemblyincluding:

-   -   a pump impeller according to either the first or fifth aspects;    -   a flow directing device according to the second or third        aspects; and    -   a pump casing according to the fourth aspect,

said impeller being mounted for rotation within said pumping chamber ofsaid main body section of said pump casing, said flow directing devicebeing operatively secured to said pump casing.

In a seventh aspect the present invention provides a method of pumping aflow of a slurry material, the method comprising the steps of:

-   -   operatively coupling (i) an impeller having one or more inducer        elements that are positioned adjacent to the impeller inlet        opening onto (ii) a flow directing device which has a passageway        for providing the in use delivery of material to the opening;        and    -   actuating the rotation of the impeller relative to the flow        directing device.

In an eighth aspect, the present invention provides a method of causingmixing and agitation of a slurry material, as well as pumping of a flowof the slurry material, the method comprising the steps of:

-   -   operatively coupling (i) an impeller having one or more inducer        elements that are positioned adjacent to the impeller inlet        opening and one or more flow generating elements that are        positioned to extend from a shroud of the impeller onto (ii) a        flow directing device which has at least one passageway for the        in use circulation of a flow of slurry material past the        impeller so as to cause mixing and agitation of the slurry        material, and a passageway for providing the in use delivery of        material to the inlet opening; and    -   actuating the rotation of the impeller relative to the flow        directing device.

In a ninth aspect the present invention provides a method of causingmixing and agitation of a slurry material, as well as pumping of a flowof the slurry material, the method comprising the steps of:

-   -   operatively coupling an impeller in accordance with the first or        fifth aspects with a flow directing device in accordance with        either the second or third aspects; and    -   actuating the rotation of the impeller relative to the flow        directing device.

In a tenth aspect the present invention provides a method of replacingan impeller in a pump assembly according to the sixth aspect, the methodincluding the steps of removing the flow directing device to therebyprovide access to the pumping chamber, removing the impeller from thepumping chamber and replacing it with another impeller and resecuringthe or another flow directing device to the pump casing.

In an eleventh aspect the present invention provides a method ofassembling a pump assembly according to the sixth aspect, the methodincluding mounting the impeller within the pumping chamber andoperatively securing the flow directing device to the pump casing.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of theapparatus, and method as set forth in the Summary, specific embodimentsof the method and apparatus will now be described, by way of example,and with reference to the accompanying drawings in which:

FIG. 1 is a schematic sectional side elevation of a typical submersiblepump apparatus with which the various components of the presentinvention are suitable for use;

FIG. 2 is an exploded view of a pump assembly according to oneembodiment of the present invention;

FIG. 3 is an isometric view of a pump casing for a pump assemblyaccording to the present invention viewed from an in use upper side;

FIG. 4 is an isometric view of the pump casing shown in FIG. 3 viewedfrom an in use lower side;

FIG. 5 is a first part sectional view of the pump casing shown in FIGS.3 and 4;

FIG. 6 is a second part sectional view of the pump casing shown in FIGS.3 to 5;

FIG. 7 is an in use top plan view of the pump casing shown in FIGS. 3 to6;

FIG. 8 is an in use underside plan view of the pump casing shown inFIGS. 3 to 7;

FIG. 9 is an isometric view of an impeller for a pump assembly accordingto the present invention viewed from an in use upper side;

FIG. 10 is an isometric view of the impeller shown in FIG. 9 viewed froman in use lower side;

FIG. 11 is an in use top plan view of the impeller shown in FIGS. 9 and10;

FIG. 12 is an in use underside plan view of the impeller shown in FIGS.9 to 11;

FIG. 13 is a side elevation of the impeller shown in FIGS. 9 to 12;

FIG. 14 is a sectional side elevation of the impeller shown in FIGS. 9to 13;

FIG. 15 is an isometric view of a flow directing device for a pumpassembly according to the invention viewed from an in use upper side;

FIG. 16 is an isometric view of the device shown in FIG. 15 viewed froman in use lower side;

FIG. 17 is an in use top plan view of the device shown in FIGS. 15 and16;

FIG. 18 is an in use underside plan view of the device shown in FIGS. 15to 17;

FIG. 19 is a side elevation of the device shown in FIGS. 15 to 18;

FIG. 20 is a sectional side elevation of the device shown in FIGS. 15 to19;

FIG. 21 is a sectional side elevation of a pump assembly according tothe invention when in an assembled position.

FIG. 22 is a perspective view of a sub-assembly of the pump apparatusaccording to the present invention; and

FIG. 23 is a perspective view of the sub-assembly of the pump apparatusshown in FIG. 22 but now including the drive motor.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring now to the drawings, in FIG. 2 a pump assembly 100 is shownwhich comprises a pump casing 30, an impeller 50 and a flow directingdevice 80. The impeller 50 is disposed within the pump casing 30 and theflow directing device 80 mounted to the pump casing to enclose theimpeller 50 therebetween when the three components are assembledtogether. In one normal mode of operation the impeller 50 is mounted forrotation about a substantially vertical axis, and the flow directingdevice 80 is disposed below the pump casing 30.

As shown in FIGS. 3 to 8 the pump casing 30 includes a pump body section32 having a pumping chamber 36 therein which is adapted to receive theimpeller 50. The pump body section 32 includes a peripheral side wall34, a back wall 38 and an open front side 42. A peripheral mountingflange 35 surrounds the open front side 42. The central axis of flange35 is axially offset with respect to the central axis of second inlet44. The open front side 42 provides for a first inlet 40 to the pumpingchamber 36. A discharge pipe 49 extends from the peripheral side wall 34and is in fluid communication with the pumping chamber 36. The pumpingchamber 36 is of a volute shape.

The pump casing 30 further includes a strainer section 46 which extendsfrom the back wall 38 of the pump body section 32. The strainer section46 and the pump body section 32 are an integral unit which may be castor otherwise suitably formed. By manufacturing the strainer section ofwear resistant material (as is the pump body section 32), the life ofthe product can be extended compared with the prior art apparatus (referto FIG. 1) in which the strainer section is made of a mesh materialwhich can become rapidly worn. The strainer section 46 is hollow and hasa generally frusto-conical side wall 43 tapering inwardly towards theback wall 38 of the pump body section 32. A mounting flange 51 isprovided at the end of the strainer section 46 remote from pump bodysection 32. A second inlet 44 provides for fluid communication betweenthe pumping chamber 36 and the interior of the strainer section 46. Asshown in FIG. 6, six elongate feed aperture slots 45 are arranged in theside wall 43 of the strainer section 46, the apertures 45 being inspaced apart relation around the side wall 43. A plurality of flowdistribution vanes in the form of twelve vertically-aligned, elongateprotrusions 47 are provided in the region of inlet 44. These protrusions47 assist the even flow of slurry material and reduce swirl in flow fromthe strainer section 46 into the pumping chamber 36 via the inlet 44.

In further embodiments of the pump casing, a different shape of strainersection other than frusto-conical can be envisaged, as well as adifferent shape of the pump body section 32, for example dome-likerather than the generally flat-topped form 32, 34 shown in the drawings.

Referring now in particular to FIGS. 9 to 14 there is illustrated animpeller 50 which, as is best illustrated in FIG. 14, comprises a hub 52having a mounting 54 for a drive shaft (not shown) and an eye 53. Theimpeller 50 is rotatable about the axis of rotation X-X. The impellerfurther includes a back shroud 56 extending from the eye 53 of the hub52 the back shroud having an inner face 57 and an outer face 58. Theimpeller further includes a front shroud 60 with an impeller opening 70extending therethrough. A plurality of pumping vanes 74 extend betweenthe shrouds 56 and 60, each vane having an inner leading edge portion 76and a trailing outer edge portion 77. The front shroud has an innersurface 62 and an outer surface 63. As shown, the front shroud 60 isgenerally curved in shape to define a projecting wall portion whichextends away from the pumping vanes 74 and which tapers in an inwardlycurved manner. The portion of the front shroud 60 which is adjacent tothe impeller opening 70 is generally coaxial with respect to therotation axis X-X. The shroud 60 has an inner edge 65 and an outer edge66, the impeller inlet opening 70 being at the inner edge 65. In thespace between the shrouds 56, 60 is a flow intake region 68 which islocated between the inner edge of the front shroud 65 and the inner edgeof the vanes 74.

The impeller also includes four further pumping vanes 78 extending fromthe outer face 58 of back shroud 56. These pumping vanes 78 aregenerally curved and arranged with one end being adjacent to the outerperipheral edge portion 77 of the back shroud 56, and the other endbeing adjacent to the hub 52. In use a material slurry which is drawninto the pump in the region of the back shroud 56 by the rotation of theimpeller 50 is pumped via these pumping vanes 78.

The impeller 50 further includes two flow inducer elements disposedcircumferentially within the flow intake region 68. The inducer elementsare in the form of inducer vanes 73 which are located on the inner face57 of the front shroud and which extend toward the axis of rotation X-X.These inducer vanes 73 help create a swirling flow which, in theapplication of a sump pump, extends from the impeller inlet towards thebottom of the sump or pit to assist the particles to be uplifted andentrained in the flow and to enter the pump impeller 50. The number,size, shape and proportion of the vanes can vary beyond the arrangementshown in FIGS. 9 to 14 in which two vanes are shown of aerofoil crosssection, angled relative to the flow into the intake, positioneddiametrically opposite one another at the impeller opening 70 andextending towards the inlet centreline by approximately 50% of theradius. The number and shape of the inducer vanes, and the angle anddistance of each relative to the centreline can be varied to optimisethe inflow to suit specific pumping needs.

The impeller 50 further includes a plurality of flow generating vanes 72extending from the outer surface of the front shroud. As illustrated sixvanes are shown around the outer surface of the front shroud. These flowgenerating vanes 72 help create a recirculating flow in the region ofthe pump inlet, aimed to cause a disturbance of any settled particulatematter in the region of the impeller which, in the application of a sumppump, can be in the bottom of the sump or pit to assist the particles tobe entrained in the flow. The number, size, shape and proportion of thevanes can vary beyond the arrangement shown in FIGS. 9 to 14 in whichsix vanes are shown of aerofoil cross section, each aerofoil beingangled relative to the flow into the intake region 68.

Referring in particular to FIGS. 15 to 20, a flow directing device 80 isshown which, as best illustrated in FIGS. 19 and 20, comprises a mainbody 81 which is comprised of an outer peripheral wall section 85 and aninner section. 86. The outer wall section 85 and inner wall section 86are interconnected by a series of flanges 87. The main body 81 has aninner side 82 and an outer side 83. The outer peripheral wall section 85is generally circular when viewed in plan and has an annular mountingflange 88 at one side thereof. A chamber 89 is provided adjacent theinner side 82 and is in communication with concentrically arrangeddelivery passageways 91 and 92 and formed by ring shaped elements 95 and96. Passageway 92 is generally annular in shape about inner passageway91. The ring shaped elements 95 are connected together by flanges. Thepassageways are generally annular in shape when viewed in horizontalcross-section and arranged substantially concentrically with respect toone another.

The device 80 further includes annular flow circulating passageways 93and 94 which provides for flow circulation between the inner and outersides of the main body 81. The passageways are generally concentric withone another, and the ends thereof being adjacent the inner side of themain body 81. The ring shaped element 96 has a skirt portion 98 whichextends beyond the other elements and aids as a partial barrier betweenthe delivery passageways 91 and 92 and the flow circulating passageways93 and 94.

In response to the in use rotation of the adjacent impeller 50, such adevice 80 can create a recirculation flow pattern of slurry materialaimed to cause the disturbance of settled particulate matter in theregion of the impeller, which can be important for clearing settledsolids from a sump pit when the particles may be large in size ornaturally heavy or dense. Slurry material can be cycled through flowpassageways 93, 94 to effect dispersal of settled particles. Once thesettled solid material is disturbed, the flow directing device 80 alsohas concentrically arranged delivery passageways 91 and 92 which lead tothe impeller. Rotation of the impeller 50 causes a pumping action whichdraws the fluidised slurry material into the impeller 50 for removal.The device 80 therefore performs a dual function and is ideally suitedto pumping applications in areas where solids may have been allowed tosettle for some time.

As best illustrated in FIG. 21 which shows the pump assembly 100 in itsinstalled position, the axis X-X which is the axis of rotation of theimpeller 50 is axially offset with respect to the central axis of theflange 35 on pump casing 30 and flange 88 on flow directing device 80. Acircular, compressible rubber seal can be incorporated between theflanges on the pump casing 30 and the device 80. The arrangement of theflanges ensures that the device 80 can only fit in one orientation withrespect to the casing 30.

In the assembled position shown in FIG. 21, the front shroud 60 of theimpeller 50 is partially disposed within chamber 89 of the flowdirecting device 80 with the flow inducer elements 73 being adjacent andin fluid communication with passageways 91 and 92 of the device 80, andthe flow generator vanes 72 being adjacent and in fluid communicationwith passageways 93 and 94.

Referring to FIG. 22 a pump sub-assembly 110 is shown including a pump100 as herein described with reference to FIGS. 2 to 21. The pumpsub-assembly 110 includes a mounting plate 125 which is secured to afloor below which the sump is located. When installed the pump apparatus100 is arranged in a generally upright orientation as shown in thedrawings, with the flow directing device 80 being disposed close to thebottom of the sump. A drive shaft 116 is operatively connected to thepump impeller 50 and is supported by a bearing assembly 118. A column120 surrounds the drive shaft 116 and an extension pipe 128 extends fromthe discharge pipe 49 of the pump casing 30.

As shown in FIG. 23 a vertically-mounted motor 134 is provided to drivethe pump drive shaft 116. The motor shaft (not shown) is operativelyconnected to pump drive shaft 116 by a vee-belt transmission. The motordrive shaft is arranged for adjustable pivotal movement relative to thepump drive shaft 116 so that the distance between the two shafts can beadjusted thereby providing for correct tensioning or re-tensioning ofthe belt. This can be effected by a one point adjustment screw which canbe adjusted by a hand tool. A cover 132 overlies the transmission andcan be readily removed to provide access to the transmission in order toadjust the belt tension, for example. A lifting frame 130 can be used tolift the apparatus by way of any suitable lifting device.

The operation of the pump apparatus will hereinafter be described. Thepump sub-assembly 110 and motor 134 is installed in an uprightorientation with the column 120 and pump assembly 100 extending into thesump and arranged so that the flow directing device 80 is adjacent thebottom of the sump where particulate matter tends to settle and buildup.

Actuation of the motor 134 causes rotation of pump drive shaft 116 andthe impeller 50 associated therewith. When the impeller 50 is rotating,the inducer vanes 73 cause flow currents which stir up the particulatematter on the bottom of the sump. In addition the flow generator vanes72 cause a circulating flow stream through the passages 93, 94 in theflow directing device 80 which add to the disturbance of the particulatematter and cause general mixing and agitation. As a result of thisaction, the disturbed particulate matter will be pumped by passingthrough the pump casing 30 and out through the outlet pipe bend 49. Thepassages in the flow directing device 80 limit the size of theparticulate matter which can pass through the pump.

When the impeller 50 becomes worn, for example, the flow directingdevice 80 can be removed and the impeller replaced with a new one beforethe (or another) flow directing device 80 is refitted to the pump casing30.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” or “comprising”, will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integers or steps.

In the foregoing description of preferred embodiments, specificterminology has been resorted to for the sake of clarity. However, theinvention is not intended to be limited to the specific terms soselected, and it is to be understood that each specific term includesall technical equivalents which operate in a similar manner toaccomplish a similar technical purpose. Terms such as “front” and“rear”, “above” and “below” and the like are used as words ofconvenience to provide reference points and are not to be construed aslimiting terms.

The reference in this specification to any prior publication (orinformation derived from it), or to any matter which is known, is not,and should not be taken as an acknowledgment or admission or any form ofsuggestion that that prior publication (or information derived from it)or known matter forms part of the common general knowledge in the fieldof endeavour to which this specification relates.

Finally, it is to be understood that various alterations, modificationsand/or additions may be incorporated into the various constructions andarrangements of parts without departing from the spirit or ambit of theinvention.

The claims defining the invention are as follows:
 1. A pump assemblyincluding: a pump impeller comprising: a hub, a back shroud extendingfrom the hub, and a front shroud, wherein each of the shrouds has aninner surface and an outer surface, the impeller also having: aplurality of pumping vanes extending between the respective innersurfaces of the shrouds, and an impeller inlet opening in the frontshroud coaxial with the rotation axis of the impeller, and wherein theimpeller includes one or more inducer elements which extend from theinner surface of the front shroud towards the rotation axis and whichare positioned adjacent the impeller inlet opening; a flow directingdevice for directing material in relation to the adjacent movingimpeller, the device including a main body having an inner side and anouter side, a plurality of passageways extending between the inner sideand the outer side of the main body, at least one passageway providingfor the in-use delivery of material to an opening of the impeller and atleast one other passageway providing for the in-use circulation of aflow of material past the impeller; and a pump casing comprising: a mainbody section having a pumping chamber therein, and a discharge outletextending from the pumping chamber; a strainer section having an intakeregion therein, with one or more inlets located at the intake region;and a feed opening between the intake region and the pumping chamber;wherein a plurality of flow distribution vanes are positioned in theregion of the feed opening; and wherein said impeller is mounted forrotation within said pumping chamber of said main body section of saidpump casing, said flow directing device being operatively secured tosaid pump casing.
 2. A pump impeller having a rotational axis andincluding: a hub; a back shroud extending from the hub; and a frontshroud; wherein each of the shrouds has an inner surface and an outersurface, the impeller also having: a plurality of pumping vanesextending between the respective inner surfaces of the shrouds, and animpeller inlet opening in the front shroud coaxial with the rotationaxis of the impeller; wherein the impeller includes one or more inducerelements which extend from the inner surface of the front shroud towardsthe rotation axis and which are positioned adjacent the impeller inletopening; and a plurality of flow generating elements arranged in aspaced apart fashion and extending from the outer surface of the frontshroud in the region of the impeller opening.
 3. A pump impelleraccording to claim 2 wherein, for a plurality of flow generatingelements, the said elements are in the form of vanes.
 4. A pump impelleraccording to claim 3 wherein the vanes are generally of an aerofoilshape.
 5. A pump impeller according to claim 3 wherein the front shroudincludes an annular wall portion and a projecting wall portion dependingtherefrom, the projecting wall portion arranged to extend away from thepumping vanes to terminate at a free end, and wherein the vanes are onthe outer surface of the projecting wall portion adjacent the free end.6. A pump impeller according to claim 2 wherein, for a plurality ofinducer elements, the said elements are arranged circumferentially aboutthe impeller inlet opening.
 7. A pump impeller according to claim 2wherein the front shroud includes an annular wall portion and aprojecting wall portion depending therefrom, the projecting wall portionarranged to extend away from the pumping vanes to terminate at a freeend, the impeller inlet opening being in the region of the free end soas to define an impeller intake region between the impeller inletopening and the pumping vanes.
 8. A pump impeller according to claim 7wherein the projecting wall portion tapers inwardly from the annularwall portion when moving in a direction towards the free end.
 9. A pumpimpeller according to claim 8 wherein the projecting wall portion iscurved.
 10. A pump impeller according claim 2 including a further groupof pumping vanes on the outer surface of the back shroud arranged inspaced relation from one another.
 11. A pump impeller according to claim10 wherein each further pumping vane is curved with one end adjacent theback shroud outer peripheral edge and extending inwardly therefromtowards the hub.
 12. A pump impeller according to claim 2 wherein, for aplurality of inducer elements, the said elements are in the form ofvanes.
 13. A pump impeller according to claim 12 wherein the vanes aregenerally of an aerofoil shape.
 14. A pump impeller according to claim12 wherein the vanes are on the inner surface of the projecting wallportion adjacent the free end.
 15. A method of causing mixing andagitation of a slurry material, as well as pumping of a flow of theslurry material, the method comprising the steps of: operativelycoupling the impeller of claim 2 with a flow directing device fordirecting material in relation to an adjacent moving impeller, thedevice including a main body having an inner side and an outer side, aplurality of passageways extending between the inner side and the outerside of the main body, at least one passageway providing for the in usedelivery of material to an opening of the impeller and at least oneother passageway providing for the in use circulation of a flow ofmaterial past the impeller; and actuating the rotation of the impellerrelative to the flow directing device.
 16. A flow directing device inuse for directing material in relation to an adjacent moving impeller,the device including a main body having an inner side and an outer side,a plurality of passageways extending between the inner side and theouter side of the main body, at least one passageway providing for thein use delivery of material to an opening of the impeller and at leastone other passageway providing for the in use circulation of a flow ofmaterial past the impeller, wherein said main body includes a peripheralside wall section and a plurality of concentrically arranged ring shapedelements operatively connected together and operatively connected to theperipheral side wall section, said passageways comprising annular spacesbetween the ring shaped elements.
 17. A flow directing device accordingto claim 16 wherein one of said ring shaped elements includes a skirtportion at the outer side of the main body which provides for a partialbarrier between a circulation passageway and a delivery passageway. 18.A flow directing device according to claim 16 further including achamber adjacent the inner side of the main body, said passagewayscommunicating with said chamber.
 19. A flow directing device accordingto claim 16 including a plurality of said delivery passageways and aplurality of said circulation passageways.
 20. A flow directing deviceaccording claim 19 wherein a plurality of said passageways are generallyannular in shape when viewed in a horizontal cross-section and arrangedsubstantially concentrically with respect to one another.
 21. A flowdirecting device according to claim 20 wherein the or each circulationpassageway is disposed radially outwardly with respect to the or eachdelivery passageway.
 22. A method of causing mixing and agitation of aslurry material, as well as pumping of a flow of the slurry material,the method comprising the steps of: operatively coupling (i) an impellerhaving an inlet opening one or more inducer elements that are positionedadjacent to the impeller inlet opening, and one or more flow generatingelements that are positioned to extend from a shroud of the impelleronto (ii) a flow directing device which has at least one passageway forthe in use circulation of a flow of slurry material past the impeller soas to cause mixing and agitation of the slurry material, and apassageway for providing the in use delivery of material to the inletopening; and actuating the rotation of the impeller relative to the flowdirecting device.